1. Field of the Invention
The invention relates to a method of fabricating semiconductor structures, and more particularly, to a method of forming liquid crystal displays (LCD) where a triple damascene technique is used to create a uniform thickness in the liquid crystal material in the manufacture of integrated circuit devices.
2. Description of the Prior Art
Liquid crystal displays (LCD) are used in the art for a variety of applications from watches to computer screens. Typically, the liquid crystal display layer is built upon an array of metal pixels. The metal pixels are formed overlying a bottom substrate. A transparent material overlies the LCD layer to form a top substrate.
FIG. 1 illustrates a LCD integrated circuit device of the prior art. A semiconductor substrate 10 is shown. An insulating layer 14 is formed overlying the semiconductor substrate 10. Metal traces 18 are formed in the insulating layer 14. Metal plugs 22 are formed to provide vias to the metal traces 18. Metal pixels 26 are then formed overlying the insulating layer 14 and contacting the metal plugs 22. A passivation layer 30 is deposited overlying the metal pixels 26. A layer of liquid crystal display material 38 is then sandwiched between the passivation layer 30 and the transparent layer 46. Glass spacers 34 maintain a gap between the passivation layer 30 and the transparent layer 46.
Several problems are encountered in the prior art LCD structure. First, because the metal pixels are formed by first depositing a metal layer and then etching it to form the pixel shapes, the quality of the pixel image is affected by the metal etch and post clean processes. Second, the large size of the metal pixels compared to the relatively small spaces between them can cause microloading effects during the metal etch process. Third, the transparent image point electrode formed by patterning the transparent layer 46 can become unsupported or can sag 42 if the glass supports land between metal lines as shown by 43. This causes the thickness of the liquid crystal material 38 to vary and the image is adversely affected. Fourth, the presence of metal sidewalls causes reflection angles 44 from the liquid crystal that can cause image problems.
Several prior art approaches disclose methods to fabricate LCD integrated circuit devices. U.S. Pat. No. 5,879,959 to Chen shows a liquid crystal display with an upper metal gate. U.S. Pat. No. 5,693,237 to Bodensohn discloses a process to form a LCD that is supported by a planarizing insulating layer surface. U.S. Pat. No. 5,614,427 to den Boer et al teaches a design for an active matrix LCD. U.S. Pat. No. 5,852,481 to Hwang shows a method for forming metal layers in a LCD.